Linear scale detection and data processing！

Linear scale detection and data processing
Sub-divisional and sentenced to law
Measuring the displacement of the substance of the grating is the grating pitch as a standard ruler to measure weightmeasuring. High-resolution grating general cost of more expensive and difficult to manufacture. In order to improve the resolution of the system, it needs to be broken down moire, the current (2006) grating sensor system to use more electronic subdivision. When the two gratings overlap with a slight dip in the grating lines substantially perpendicular to the direction of moire fringes, with the movement of the grating, moire also will move up and down. This put the measure on the grating pitch is converted to the measurement of the number of Moire fringes.
In a moire width, according to certain spaced four photovoltaic device can achieve sub-divisional and sentenced to function. For example, the gate line 50 line pairs / mm grating, the grating pitch of 0.02mm, the use of a four-segment resolution is obtained after counting pulses 5μm, which has reached a high in general industrial measurement and control accuracy. Since the displacement is a vector, that is, to detect its size, but also to detect its orientation, and therefore requires at least two different phases of photoelectric signals. In order to eliminate common mode interference, DC component and even harmonics, usually low-drift op amp differential amplifier configuration. 4 photoelectric signal obtained by the four photosensitive devices were sent to the amplifier input 2're just minutes from the two differential amplifier output signal whose phase difference π / 2, in order to obtain and sentenced to count pulse, the need for two-way signal shaping, shaping them for the first duty ratio of 1: 1 square wave. Then, the phase of the square wave discriminate comparison, you can wait until the moving direction of the grating. By counting the square wave pulse, you can wait until the scale of the displacement and velocity. [2]

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